1. Field of the Invention
The present invention relates to a light emitting diode (LED) lamp including an LED unit mounted on a light source substrate.
2. Related Art
A related art LED lamp has a shape like an incandescent lamp. The LED lamp has a lamp body, a base provided on one end of the lamp body, a light source substrate provided on the opposite side of the lamp body from the base, an LED unit mounted on the light source substrate, and a light transmissive cover arranged to cover the LED unit. The LED unit has an LED chip that emits blue light, and a resin portion that covers the LED chip. Phosphors absorbing a part of the blue light and emitting yellow light are mixed in the resin portion, so that the LED unit emits white light by the mixture of the blue light and the yellow light (see, e.g., JP 2010-033959 A).
According to another related art, an LED unit has an LED chip that emits blue light, an encapsulation resin containing yellow light emitting phosphors, and a cup-shaped opaque container accommodating the LED chip and the encapsulation resin. The inner surface of the container is configured as a reflecting surface to enhance light mixture of multiple colors, thereby radiating white visible light having a strong directivity (see, e.g., JP 10-107325 A).
According to an LED unit configured to intensify the directivity of visible light, the amount of light from the LED chip toward the circumference of the LED unit is low, resulting in low illuminance in the region lateral to the lamp. For example, as illustrated in FIG. 6, with respect to 1 being the illuminance in the radiation angle of 0° (directly below the lamp unit), relative illuminance lowers as the radiation angle becomes wide, and may become 0 in the radiation angle of 90° (directly lateral to the lamp unit).